Ecological Threat: Purple loosestrife adapts readily to natural and disturbed wetlands. As it establishes and expands, it outcompetes and replaces native grasses, sedges, and other flowering plants that provide a higher quality source of nutrition for wildlife. The highly invasive nature of purple loosestrife allows it to form dense, homogeneous stands that restrict native wetland plant species, including some federally endangered orchids, and reduce habitat for waterfowl.

Biology & Spread: Purple loosestrife enjoys an extended flowering season, generally from June to September, which allows it to produce vast quantities of seed. The flowers require pollination by insects, for which it supplies an abundant source of nectar. A mature plant may have as many as thirty flowering stems capable of producing an estimated two to three million, minute seeds per year.

Purple loosestrife also readily reproduces vegetatively through underground stems at a rate of about one foot per year. Many new stems may emerge vegetatively from a single rootstock of the previous year. "Guaranteed sterile" cultivars of purple loosestrife are actually highly fertile and able to cross freely with purple loosestrife and with other native Lythrum species. Therefore, outside of its native range, purple loosestrife of any form should be avoided.

History: Lythrum salicaria derived it?s name from a Greek medical man in Nero?s Roman army when he called the plant Lytron, Greek for blood. Awareness of the medicinal properties or the flowering spike resemblance to blood or gore from a wound led to the name. The similarity of loosestrife leaves to those of the willow (Salix spp.) resulted in the species name of salicaria. (Balogh 1986).
The first North American record of purple loosestrife was in wet Canadian meadows and in New England, as recorded in Pursh?s Flora Americae Septentrionalis, in 1814. (Louis-Marie 1944 as cited in Balogh 1986). It was first recorded as a problem weed in Quebec in the 1930?s. By 1942, a pasture that at one time supported 800 head of cattle was declared useless. (Balogh 1986).

U.S. Habitat: Purple loosestrife occurs in freshwater and brackish wetlands. It is a successful colonizer and potential invader of any wet, disturbed sites in North America. Associated species include cattails, rushes, sedges, and reeds.

Distribution

U.S. Nativity: Introduced to U.S.

Native Origin: Europe (NatureServe Explorer); Old World (Bailey, L.H. and E.Z. Bailey, Hortus Third: A Concise Dictionary of Plants Cultivated in the United States and Canada, MacMillan Publishing Co., Inc., New York , (1977).)

Distribution: Europe and Asia are thought to be the geographic origin of purple loosestrife. The European populations cover the greatest range. The main islands of Japan are the core of the Asian native range. L. salicaria is now circumpolar in the northern hemisphere, and the distribution range also includes other temperate and subtropical areas, including: eastern Africa, Australia, Tasmania, and New Zealand. (Thompson et al. 1987).
Thompson, D.Q., R.L. Stuckey and E.B. Thompson. 1987. Spread, Impact and Control of Purple Loosestrife (Lythrum salicaria) in North American wetlands. USFWS, Fish and Wildlife Research No. 2. US DOI, Washington, D.C. 55pp.

Management

Purple loosestrife also spreads vegetatively. Buried stems harbor adventitious buds with the ability to produce shoots or roots. Disturbance to the plant, such as stomping and breaking underground stems, or breaking off stems or roots during incomplete plant removal, does initiate bud growth. Cutting alone is not a control option for purple loosestrife. Shoots and adventitious roots will develop. Cutting late in the season reduced shoot production more than mid summer cutting, indicating that carbohydrate reserves could not be restored for next years growth.

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